I still am starting out. I've only sold a couple of my current product on eBay and the first one I sold, I put it in a box and put some bubble wrap in it for protection. I charge a flat rate of $7.00 for shipping. With that shipping method, I was charged more than $5.00 to ship the product. I decided to try putting the product in a bubble mailer, I just got back from the store and it only cost me $2.66!
So to help beginners, I would just say to test things out and try different things when you're starting out and see what works.